What will happen if DC motor is used without starter? Explanation: It would cause intolerably heavy sparking at the brushes which may destroy the commutator and brush-gear. … Explanation: In shunt and compound motors starting the shunt field should be switched on with full starting resistance in armature circuit.
Why are starters required in a DC motor?
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.
Why is a starter motor necessary?
A motor starter provides defense by first controlling the electrical output of your device or equipment at its initial point of operation (when you turn it on or it engages). From that point, the starter continues to protect your system, operating as a fail-safe.
What is the function of the motor starter with respect to current?
Explanation: The main function of the starter is to prevent excessive current flow. At the same time it should allow current to produce good or high starting torque.
What will happen if the back EMF of DC motor vanishes?
If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.
Which starter does not provide high speed protection to the DC shunt motor?
Four point starter does not provide high speed protection to d.c. shunt motor.
Where is DOL starter used?
The applications of DOL starters are primarily motors where a high inrush current does not cause excessive voltage drop in the supply circuit (or where this high voltage drop is acceptable). Direct on line starters are commonly used to start small water pumps, conveyor belts, fans, and compressors.
What happens if motor back emf is 0 no current flows?
So, if back emf is zero that means which tells us that either speed of the motor or field flux or both are zero. In other words, the motor is standstill because field flux is required for creating torque for rotation. So, if E=0, the supplied voltage equals to voltage drop against armature resistance.
What will happen to a DC motor if its back emf is equal to the supply voltage?
As the back emf depends on the current their value also decreases. The magnitude of the back EMF is nearly equal to the supply voltage. If the sudden load is applied to the motor, the motor becomes slow down. As the speed of the motor decreases, the magnitude of their back emf also falls down.
What happens if DC motor is connected to AC supply?
When AC supply is given to DC series motor:
An AC supply will exert unidirectional torque because the direction of armature current and field current reverses at the same time and the direction of rotation will as it is.